Electrolyte abnormalities Flashcards
Overview of causes of electrolyte imbalances
- Renal
- Endocrine
- Gastrointestinal
- Skin
Treatment priority
- pH
- Potassium
- Calcium
- Magnesium
- Sodium
- Chloride
Etiology of hypernatremia
\++Sodium 1. Conn's syndrome Hypokalemia, alkalosis,hypertensive \++loss of sodium:water 1. Fluid loss without water replacement Diarrhea Vomiting Burns 2. Incorrect IV replacement 3. Diabetes insipidus 4. Osmotic diuresis -> DKA
Management of hypernatremia
- Oral fluid replacement - water if possible
- If not, IV 5% dextrose, guide by urine
- Do not decrease sodium by >0.5mmol/L / h or 10mmol/L / 24h
- If hypovolemic->may use NS
- Avoid hypertonic solutions
Calculating decrease in serum sodium/ L 5% glucose
][Serum sodium]/ TBW + 1
TBW= 0.6 in men, 0.4 in women
Etiology of hyponatremia
Check plasma osmolality
1. Factitious
->N osmolality= +lipids, proteins (MM)
->+Plasma osm= osmotic solutes drawing in= glucose, urea (hypertonic)
->Pseudohyponatremia
2. Hypoosmolar
a. Euvolemic
R: Drugs (lots of them….like NSAIDS, TCA’s, Carbamazepine)
E: ↓ Thyroid
G: H2O Intoxication (psychogenic polydipsia)
S: S.I.A.D.H. ( Nothing to do with skin this time)
b. Hypervolemic (+Na, +H20)
R: ARF, Nephrotic syndrome
E: ↑ Aldo (eg. CCF)
G: Cirrhosis (low albumin/protein)
S: I.V. Fluids (too much hypotonic stuff eg 5% Dextrose)
c. Hypovolemic (low sodium, low water)
R: diuretics, RTA, ARF, nephritis
E: Addisons, low aldosterone, osmotic diuresis
G: DV, fistula, NGT, pancreatitis
(3rd space occupation,)
S: sweat, burns
Clinical features
- Anorexia, nausea, malaise initially
- HA, irritability, confusion
- Weak, -ve GCS, seizures
- Determine if deH or not
- Edema?
Iatrogenic hyponatremia
- Infusion of 5% dextrose
- Metabolised->hypotonic fluid
- Hyponatremia
- +Risk for those on diuretics, elderly, physiologic stress
Management of hyponatremia
- Correct the underlying cause
- If mild, chronic->fluid restriction
- If severe seek expert help
IV 3% saline, target not >120 initially - Moderate
Fluid restriction 500ml-1L/24 h
Monitor serum/electrolytes/urine output daily
May consider demeclocycline (ADH antagonist) - Volume depletion
NS w/ potassium - If hypervolemic
Can consider vaptans->excretion of electrolyte free fluids
What is the concern with rapid correction of hypernatremia, risks, how to avoid
- Permanent central nervous system injury due to osmotic demyelination
- Those w. chronic +
10mmol (/L in first 24 hour
X +>18mmol/L in first 48 hours
Goal therapy +4-8mmol/L
When could more rapid correction in hypernatremia occur
- Seizures or coma
- Self induced acute water intoxication
- Known hyponatremia for
Pathogenesis of CNS damage with rapid sodium correction
- Cerebral shrinkage endothelial- +BBB permeable,
cytokines enter brain - Cell water shrinks, potassium and cations enter cells
Calculation infusion rate of NaCl 3%- use a 60kg woman, with serum sodium 110, want to be 118
- calculate desired increase
in 24 hours. Say current = 110, want to
be 118 in 24 hours= 8mmol/L increase over 24 hours - Increase in Na/L of infused 3%= 513- Na serum mmol/L/
TBW + 1 (TBW= wt X 0.5 (female), 0.6 (male), elderly 0.45, 0.5 - 13mmol/L of 3% increase over 24 hours
so 8/13 X 100= 615ml of 3% to +by 8mmol. 25ml/hour of solution If already given boluses need to deduct from total infusion amount
Etiology of hyperkalemia
1. Pseudo Hemolysed From IV arm \+WCC 2. Shift Acidosis: decrease in Na/K pump= -ve IC K and +ECF K->low conc in tubular cell = reduced diffusion in tuular lumen = accumulation of K in body. Exercise Low insulin Digoxin toxicity Hyperkalemic periodic paralysis 3. Load= +external K Supplements Blood transfusion Rhabdomyolysis Hemolysis Suxamethonium 4. Loss Renal failure, burns K sparing diuretics, ACEi -ve aldosterone->Addisons
ECG changes in hyperkalemia
- +K in ECF= MP less -ve, closer to threshold= +excitability but -ve Na channels open= -ve automaticity
- Short QT interval
- Tall T waves
- Arrythmias
- Wide QRS
- P waves disappear
- QRS sine wave and asystole/VFib
